The Economic Behavior of Street Opiate Project is a quantitative and ethnographic study of the routine income, expenditures, drug use, and criminal activities of street opiate users in East and Central Harlem. Two years of pilot research showed that such data could be systematically obtained at a storefront field station in a major narcotics copping area staffed by indigenous fieldworkers and professional social scientists. During the third year, (1980), respondents have been interviewed on daily and weekly schedules. A census of active street opiate users was conducted in East Harlem. As representative a cross-section sample of narcotics users as possible is interviewed; several subjects are being followed longitudinally. New measuring techniques and knowledge are being developed. Varying patterns of opiate use and criminality are found; significant insights about the street drug trade emerge. Most respondents have incomes from various nondrug crimes (shoplifting, burglary, robbery, etc.), or from the direct sales of drugs and from steering touting, and copping drugs for others. Relatively little income is derived from employment or welfare. Free meals and lodging provided by family and friends permits most subjects to subsist without significant expenditures for normal living costs. Most of their cash expenditures go for drugs, mainly heroin and cocaine.